Scientists at the University of Missouri School of Medicine in the US have developed a procedure to detect potential false-positive Covid-19 test results.

The new process is expected to help laboratories avoid unnecessary quarantining and repeated testing of non-infected people.

The university scientists have developed a quality control procedure for detecting false-positive Covid-19 results from the reverse transcriptase-polymerase chain reaction (RT-PCR) test.

This test is considered reliable and has been the most widely used method for virus testing during the Covid-19 pandemic.

However, a small number of false-positive results have been delivered by the test, often found in asymptomatic and nonexposed patients.

University of Missouri School of Medicine pathology and anatomical sciences professor and molecular diagnostics laboratory director Lester Layfield said: “False-positive diagnoses have important implications for patient management.

“False positives may lead to inappropriate quarantine, delay of other necessary medical treatment or transfer to a Covid-19 ward.”

Layfield and his research team started repeat testing of all SARS-CoV-2 positive results from asymptomatic and unexposed patients to ensure the accuracy of positive tests.

By implementing the quality control protocol, they have retested all specimens from asymptomatic or unexposed persons with SARS-CoV-2 positive test results which were stored next to a specimen with a high viral load.

Last September, the researchers’ team implemented the quality control protocol on 24,717 RT-PCR tests over an eight-week period.

Of the total, 6,251 of the RT-PCR tests were from asymptomatic patients. 288 of these specimens delivered positive results.

During the second test, 20 of the specimens were false positives.

Layfield added: “Retesting of positive results from asymptomatic individuals revealed some technologist errors but also contamination from positive specimens in adjacent specimen wells.

“This study should alert the laboratory testing community of the possibility of false-positive Covid-19 tests.”